Heterojunction bipolar transistor and method for fabricating the same
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsTakeshi Takagi, Koichiro Yuki, Kenji Toyoda, Yoshihiko Kanzawa
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Abstract
A heterojunction bipolar transistor is fabricated by stacking a Si collector layer, a SiGeC base layer and a Si emitter layer in this order. By making the amount of a lattice strain in the SiGeC base layer on the Si collector layer 1.0% or less, the band gap can be narrower than the band gap of the conventional practical SiGe (the Ge content is about 10%), and good crystalline can be maintained after a heat treatment. As a result, a narrow band gap base with no practical inconvenience can be realized.
Claims28
A heterojunction bipolar transistor comprising a first semiconductor layer made from semiconductor material containing Si as a component;
- a second semiconductor layer made from semiconductor material containing Si, Ge and C as components, having a band gap narrower than the first semiconductor layer and consisting of a top layer, a center layer and a bottom layer, the center layer having a different composition of Ge or C or a different concentration of impurities as the top or the bottom layer;
- a third semiconductor layer made from Si as a component, and having a band gap wider than the second semiconductor layer stacked in this order onto a substrate;
- and a heterojunction barrier provided between the first semiconductor layer and the second semiconductor layer,
- said heterojunction bipolar transistor further comprising:
- a collector layer formed in the first semiconductor layer and containing a first conductive impurity;
- a base layer formed in the second semiconductor layer and containing a second conductive impurity;
- and
- an emitter layer formed in the third semiconductor layer and containing a first conductive impurity.
Dependencies are inferred from the claim text.